This invention relates to electrical connectors and particularly to connectors of the type known as power adapters for connecting electrical power to a coaxial cable for transmission of the power along the cable.
Coaxial cables are extensively used for transmitting high frequency signals. Over long distances, the signal being transmitted becomes attenuated and, to counteract this, the cable is periodically passed through repeater stations where the signal being transmitted is amplified and then transmitted along a next leg of the transmission path. The repeater station consumes electrical power, and one practice is to use the coaxial cable itself for transmitting power to the repeater stations.
Coaxial cables comprise a central electrical conductor surrounded by an electrical insulator sheath surrounded, in turn, by an outer, tubular electrical conductor. The outer conductor serves as a grounded electrical shield for the high frequency signal transmitted along the central conductor. Electrical power, e.g., d.c. or extremely low a.c. frequency power, is transmitted along the cable using the central and outer conductors as a two wire power transmission system.
In one arrangement, a coaxial cable is terminated within a portion of a repeater station known as a power inserter comprising a metal box containing various electrical components, e.g., an RF signal amplifier. The box is hermetically sealed for protecting the components from dirt and moisture. The coaxial cable terminates in a coupler, e.g., a male coupler providing an elongated prong insulated from and extending axially from an end of a metal tube having, for example, an internal screw thread. The elongated prong is electrically connected to the central conductor of the coaxial cable and the threaded metal tube is electrically connected to the outer tubular electrical shield of the cable. The metal box is provided with a terminal port comprising an externally threaded tube hermetically sealed around an opening through the box wall and extending away from the wall.
The coaxial cable is electrically and mechanically connected to the box port by inserting the coupler prong axially through the port tube while screwing the coupler internally threaded metal tube onto the externally threaded port tube. The threaded engagement of the two tubes electrically connects the cable outer electrical shield to the box metal wall while providing an hermetically sealed mechanical coupling between the cable and the box. The coupler prong extends through the port opening into electrical contact with a terminal within the box for electrically connecting the cable central conductor to the box internal terminal.
In addition to connecting the coaxial cable to the power inserter portion of the repeater stations, it is also necessary to connect electrical power to at least some of the stations. This is done by means of connectors, known as "power adapters", for connecting power supplies to the stations. Such power adapters comprise a coupler similar to the known coaxial male end couplers in that they comprise a metal prong insulated from and extending axially through and beyond a threaded metal tube. The metal tube is rigidly mounted on a tubular insulator. The prong is part of an elongated rod which extends entirely through the insulator and is exposed rearwardly thereof.
In use, the known power adapter is threaded onto a threaded tubular port member for hermetically sealing the power adapter to the metal box while disposing the adapter prong inwardly of the box and in electrical contact with a terminal therein. One wire of a two wire power supply is mechanically and electrically connected to the rearwardly extending end of the adapter central conductor for electrically connecting the wire to the internal terminal. The other wire of the power supply is directly screwed to the box wall for providing a common ground connection between the power supply and components within the box.
The present invention is directed to a power adapter somewhat similar to the described known adapters except providing certain advantages described hereinafter.